Aromatic copolyester

Abstract

An aromatic polyester copolymer consisting of 10 to 90 mol % of a recurring unit of the formula: ##STR1## and 90 to 10 mol % of a recurring unit of the formula: ##STR2## and having a logarithmic viscosity number of at least 0.3 as measured in a mixture of phenol and tetrachloroethane (6:4 in weight ratio) at a concentration of 1 g/100 cc at 25° C. and having a terminal carboxyl content of about 80 mol eq./ton or less. This aromatic polyester copolymer has high durability under dry and moist heat as well as high resistance to water crazing and hence can be fabricated into useful articles by various molding techniques.

What is claimed is: 
     
       1. An aromatic polyester copolymer consisting essentially of about 10 to about 90 mol% of a recurring unit of the formula (a): ##STR6## wherein --X-- is selected from the group consisting of --O--, --S--, --SO 2  --, --SO--, --CO--, an alkylene group containing 1 to 4 carbon atoms and an alkylidene group containing 1 to 4 carbon atoms; and R 1 , R 2 , R 3 , R 4 , R' 1 , R' 2 , R' 3  and R' 4 , which are the same or different, each is selected from the group consisting of a hydrogen atom, a chlorine atom, a bromine atom and an alkyl group containing 1 to 4 carbon atoms; and about 90 to about 10 mol% of a recurring unit of the formula (b): ##STR7## wherein --X--, R 1 , R 2 , R 3 , R 4 , R' 1 , R' 2 , R' 3 , and R' 4  have the definition in formula (a); and having a logarithmic viscosity number of about at least 0.3 as measured in a mixture of phenol and tetrachloroethane (6:4 in weight ratio) at a concentration of 1 g/100 cc at 25° C. and a terminal carboxyl content of 16 mol eq./ton or less. 
     
     
       2. The aromatic polyester copolymer of claim 1, which has a terminal carboxyl content of about 10 mol eq./ton or less. 
     
     
       3. The aromatic polyester copolymer of claim 1, which has a terminal carboxyl content of about 5 mol eq./ton or less. 
     
     
       4. The aromatic polyester copolymer of claim 1, which consists of 10 to 90 mol% of a recurring unit of the formula: ##STR8## and 90 to 10 mol% of a recurring unit of the formula: ##STR9## 
     
     
       5. The aromatic polyester copolymer of claim 1, wherein said copolymer comprises about 30 to 70 mol% of the recurring unit of the formula (a) and about 70 to 30 mol% of the recurring unit of the formula (b). 
     
     
       6. The aromatic polyester copolymer of claim 1, wherein said repeating unit of the formula (a) and said repeating unit of the formula (b) are present in said copolymer in a mol ratio of about 1:1. 
     
     
       7. The aromatic polyester copolymer of claim 1, wherein said copolymer has a logarithmic viscosity of about 0.4 to 0.8. 
     
     
       8. A polymeric composition comprising the aromatic polyester copolymer of claim 1 and an additive. 
     
     
       9. A film prepared from the aromatic polyester copolymer of claim 1. 
     
     
       10. A film prepared from the composition of claim 8, wherein said film is uniaxially or biaxially oriented. 
     
     
       11. A fiber prepared from the aromatic polyester copolymer of claim 1. 
     
     
       12. A molded article prepared from the aromatic polyester copolymer of claim 1.